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PostPosted: 30 Jun 2014, 01:09 
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Joined: 08 Aug 2009, 03:11
Posts: 2229
Location: Chilliwack, BC
WA2YNE wrote:
Seems the school system will toss older stuff, rather than contribute it to anyplace.


Custodian buddy salvaged a pickup truck full of good, working Tek 60MHz oscilloscopes that way for peanuts when a school went digital :smoking:

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PostPosted: 30 Jun 2014, 10:18 
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Joined: 17 Jun 2014, 14:49
Posts: 11
Geek wrote:
WA2YNE wrote:
Seems the school system will toss older stuff, rather than contribute it to anyplace.


Custodian buddy salvaged a pickup truck full of good, working Tek 60MHz oscilloscopes that way for peanuts when a school went digital :smoking:

That reminded me.
I have a dual trace 30+ Mhz scope that I need to see if I cn figure out a problem with, and also an older small simple scope i picked up from a guy selling some stuff,tailgating in an empty lot. Paid like $5.00 for it, maybe a bit more, as a gamble, and when I checked, it seemed to work fine.
I will point out that a simple scope can be useful for audio work.
Back when I was working on car radios and such, was a unit that had an odd distortion.
Don't recall what it sounded like, but on a scope, a simple audio sine wave had a part where it flatlined and moved over a bit.
Turned out the problem was incorrect bias on an output transistor. Matter of a resistor of a low ohm rating was bad.
replacing that corrected the distortion and the sine wave was perfect.
A scope can be very useful to locate the part of a circuit where the distortion starts.
Tube or solid state matters not.

From the stuff I salvaged from the dump here, I have so many line cords, I can repurpose some.
no need to buy any.
Also a lot of cat5 cable, though some seemed to be bad, maybe ends.
I can replace ends, once I locate where I put the tool and ends I bought and never used.
My thought is to add cat5 wiring in the house, being as i have a supply of outlets bought super cheap at a thrift store, and also a few surface mount cat5 outlets from a closeout table....
Not that I use cat5 that much now.
Mostly for testing older computers I have. Newer ones have, or I can install, wireless G.

back to my project now:
How do I upload pix here?
Or do I need to put them on my web site?
:nuke: :2c:


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PostPosted: 02 Jul 2014, 18:22 
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Joined: 17 Jun 2014, 14:49
Posts: 11
Planning coming along.
I have two possibilities for audio out[put.
One is to use the transformer from a junk 5 tube AC/DC receiver.
That is supposedly 3.2 ohm output, which used to be the common speaker rated impedence.
I already know one can feed that to a headphone, 8 ohm, or even high impedence, as I did so in the past.
Another was to use a small power transformer, saw a circuit using a 120VAC to 6.3VAC as audio output.
Being as the base I am reusing has 3 sockets, I can do something like this.
Start with just regen detector.
Add an audio stage to that maybe two, being as a 12ax7 or a 12au7 can handle up to a watt of power, should be good for headphone or small speaker.
The junk radio gives me output transformer, and a few resistors., maybe a filter cap as well.
It did not work, somewhere is an open in filaments, maybe bad socket connection.
And a lot of mouse damage.
I should be able to salvage the variable cap. Volume control, maybe as well.
osc coil may be okay, only need to figure out exactly the connections it really has, and if it is one tapped winding or two windings. It would work in BC band with right caps. rather compact coil.
The tuning cap from the junk radio is mounted on a secondary metal mount, rather than directly to the chassis as was common.
that gives me a 365 mmfd variable cap
other variable caps I have are not bigger than 100 at best.
Only one is marked, some have part number, and some unmarked.
only one with rating marked is 2.7 to 19.6.
others look like they rage from 10 or 15 max to maybe 50 or so.
And one butterfly
Not sure what to do with it...

nayway, start with detector, and maybe one audio amp
possibly and untuned cathode follower RF amp, so antenna sway and such does not affect the tuning.
Try one thing and add as I go.
sticking to the use of two to 3 dual triodes that I have.
Use an SO239 as antenna connector, which simplifies matters
I have a manual antenna tuner that also might be useful.
It smoked a bit once transmitting, never did find where the smoke escaped from
but it should serve s an RX tuner anyway. It may well have been abused before I got it in a trade.
Wound up buying a new auto tuner (can also be manually tuned by using swutches and going in part by how weel signals are received...

More to fllow.

wayne WA2YNE


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